Table 1.

Descriptive statistics for urinary 1-OHPG, indoor PM, and indoor air nicotine concentrations.

	1-OHPG (pmol/ml)	1-OHPG (µmol/mol Cr)	Indoor PM2.5 (µg/m3)	Indoor PM10 (µg/m3)	Indoor PM2.5–10 (µg/m3)	Air nicotine (µg/m3)
Number of samples	594	594	309	308	280	346
Arithmetic mean (SD)	1.76 (1.92)	0.17 (0.22)	28.4 (22.8)	41.1 (29.0)	12.7 (14.3)	0.76 (1.26)
Geometric mean	0.89	0.09	21.8	33.3	9.0	0.17
Median (IQR)	1.24 (0.42–2.43)	0.11 (0.05–0.22)	21.6 (13.0–34.9)	32.6 (21.6–52.5)	9.8 (5.4–15.8)	0.13 (0.03–0.96)
95 Percentile	5.4	0.54	72.1	97.5	30.8	3.4
Range	0.05–14.59	0.003–2.13	3.7–133.2	5.8–268.8	0.71–215.3	0.005–8.8
% Below LOD	11%	11%	–	–	–	–

	All samples	Boys	Girls	P-valuea	P-valueb
Time spent in the home
Avg. time spent in the home on days 0–6 (Sat–Fri)	16.1 (13.6–18.1)	15.9 (12.7–18.0)	16.4 (14.7–18.3)	0.067	0.161
Avg. time spent in the home on days 0–2 (Sat–Mon)	17.0 (13.7–20.3)	16.7 (11.5–19.5)	17.8 (14.3–20.3)	0.059	0.089
Avg. time spent in the home on days 4–6 (Wed–Fri)	15.7 (13.7–17.7)	15.6 (14.0–17.6)	15.7 (13.7–18.0)	0.733	0.704
Difference between days 0–2 and days 4–6c	P = 0.005
Time spent outdoors
Avg. time spent outdoors on days 0–6 (Sat–Fri)	1.9 (0.7–3.9)	2.1 (0.8–4.7)	1.6 (0.7–3.3)	0.053	0.028
Avg. time spent outdoors on days 0–2 (Sat–Mon)	2.0 (0.5–4.3)	2.0 (0.7–5.3)	1.7 (0.3–3.7)	0.053	0.033
Avg. time spent outdoors on days 4–6 (Wed–Fri)	1.5 (0.3–4.0)	1.9 (0.7–4.3)	1.0 (0.3–3.3)	0.026	0.044
Difference between days 0–2 and days 4–6 c	P = 0.404

Average time (hours) spent in the home and time spent outdoors (median (IQR)), and differences by gender.

^aWilcoxon rank-sum test for difference by gender.

^bMultivariable linear regression with GEE: adjusted for age and season.

^cWilcoxon signed-rank test. Bold value is statistically significant (P < 0.05).